This research is the advanced and extended (4-12) research based on our already developed X-ray image plate which Is composed of the X-ray fluorescent material layr and the photosensitive material layr laminated on the supporting plate. The X-ray fluorescent material layr is made of the gadolinium phosphor and the photosensitive material layr is made of the phtalocyanine organic photoreceptor. The aim of this research is to drastically lowers the X-ray dose to the object, while obtatinig an adequate image quality. The main item of this research is to cause the electron multiplication by avalanche effect in the photoreceptor layr. This electron multiplication effect is observed in a calcogenite system material such as As_2S_3 with an electric internal strong field. This practical application is already realized in the photosensitive target of the TV pick up tube in the name of Harpicon. By applying this material for the photoreceptor to the fluorescent image on the phosphor screen, the
… Moresufficient change of the surface potential is made to be obtainable even with a small dose of X-ray.Since the head investigator had moved to this Nagano NCT from the hitherto joined Reseach and Development Center of Toshiba Corp. in 1993, research started in this Nagano NCT from the zero level including the various kinds of needed measurement apparatus such as X-ray generator, both photosensitive and phosphor material handling machines and also PC.By the fund of the grant aid in 1995 and 1996, X-ray generator and the experimental zeroradiographic measurement equipment have been obtained. The high speed PC which was bought by the fund of the final year 1997 enabled us to reach to the following research results :2) By optically prohecting the X-ray stimulated fluorescent image on the scintillator, the material of which includes from ZnS to Gd_2O_2S system to the target of the TV pick up tube which multiplies the photogenerated electrons by the avalanche effect (TM : Super Harpicon), the conversion efficiency from the X-ray to the TV signal was compared. From this experiment, it has been clarified that the target of this TV pickup tube with calcogenite system shows a slightly higher sensitivety to ZnS than Gd_2O_2S instead of the hitherto considered assumption, and that the ZnS scintillator-calcogenite material photoreceptor laminated layr which enables the optical direct coupling without lens system will attain the adequate high sensitivity to the lowest X-ray dose level of the order of micro-roentgen per minute.2) The electron multiplication by avalanche effect is hitherto realized only in the vacuum of the TV pickup tube, but not has been observed in the atmospheric pressure. By the experimental setup to arrange a high voltage mesh electrode just behind the photorecepttor with 0.5mm spacing during the X-ray radiation, the high voltage difference and the mesh spacing show a great correlation to the sensitivity and the edge effect of the image signal and that this mesh effect gives the lst step to overcome to cause the avalanche effect in the atmospheric pressure. Less